1. Field of the Invention
The present invention relates to a thin film type solar cell, and more particularly, to a thin film type solar cell with a large light-transmission area, which can be used as a substitute for a glass window in a building.
2. Discussion of the Related Art
A solar cell with a property of semiconductor converts a light energy into an electric energy.
A structure and principle of the solar cell according to the related art will be briefly explained as follows. The solar cell is formed in a PN-junction structure where a positive (P)-type semiconductor makes a junction with a negative (N)-type semiconductor. When a solar ray is incident on the solar cell with the PN-junction structure, holes (+) and electrons (−) are generated in the semiconductor owing to the energy of the solar ray. By an electric field generated in a PN-junction area, the holes (+) are drifted toward the P-type semiconductor and the electrons (−) are drifted toward the N-type semiconductor, whereby an electric power is produced with an occurrence of electric potential.
Solar cells can be largely classified into a wafer type solar cell and a thin film type solar cell.
The wafer type solar cell uses a wafer made of a semiconductor material such as silicon. In the meantime, the thin film type solar cell is manufactured by forming a semiconductor in type of a thin film on a glass substrate.
With respect to efficiency, the wafer type solar cell is better than the thin film type solar cell. However, in the case of the wafer type solar cell, it is difficult to realize a small thickness due to difficulty in performance of the manufacturing process. In addition, the wafer type solar cell uses a high-priced semiconductor substrate, whereby its manufacturing cost is increased. For the wafer type solar cell, it is difficult to obtain a light-transmission area therein, so that the wafer type solar cell can not be used as a substitute for a glass window in a building.
In the meantime, even though the thin film type solar cell is inferior in efficiency to the wafer type solar cell, the thin film type solar cell has advantages such as realization of thin profile and use of low-priced material. Accordingly, the thin film type solar cell is suitable for a mass production. In addition, since the thin film type solar cell can obtain a light-transmission area with easiness, the thin film type solar cell can be used as a substitute for a glass window in a building.
Hereinafter, a related art thin film type solar cell will be described with reference to the accompanying drawings.
FIG. 1 is a perspective view illustrating a related art thin film type solar cell.
As shown in FIG. 1, the related art thin film type solar cell includes a substrate 10; a plurality of front electrodes 20; a semiconductor layer 30; and a transparent conductive layer 40. At this time, the plurality of front electrodes 20 are formed at fixed intervals on the substrate 10, and then the semiconductor layer 30 and the transparent conductive layer 40 are sequentially formed on the plurality of front electrodes 20. Also, each contact portion 35 and each separating channel 55 are formed in the semiconductor layer 30 and the transparent conductive layer 40. Then, a plurality of rear electrodes 50 are formed on the transparent conductive layer 40. Each rear electrode 50 is electrically connected with the front electrode 20 by the contact portion 35, and the plurality of rear electrodes 50 are formed at fixed intervals by each separating channel 55 interposed in-between.
However, the related art thin film type solar cell when being used as the substitute for the glass window in the building has the following disadvantages.
In order to use the thin film type solar cell as the substitute for the glass window in the building, it is necessary for the thin film type solar cell to obtain the light-transmission area therein at any size. Since the related art thin film type solar cell includes the front electrode 20 using transparent metal and the rear electrode 50 using opaque metal, the light-transmission area is limited to the separating channel 55 positioned between each of the rear electrodes 50. Accordingly, the limited light-transmission area in the related art type film type solar cell can not secure a wide visible range.
To widen the light-transmission area, the separating channel 55 positioned between each of the rear electrodes 50 may be increased in its width. This method may cause problems of lowering cell efficiency and increasing process time. That is, if increasing the width of the separating channel 55, an effective area for production of cell power, is decreased by the increased width of the separating channel 5, this can lower the cell efficiency. Also, the separating channel 55 is formed by a laser scribing process, whereby the laser scribing process has to be performed repetitively to increase the width of the separating channel 55, thereby causing a problem of long process time.